Self-healing hyperbranched polytriazoles prepared by metal-free click polymerization of propiolate and azide monomers

Article abstract of DOI:10.1007/s11426-016-0251-y

The last decade has witnessed the quick develop of self-healing materials. As a newborn strategy, the alternative of irreversible covalent bond formation is, however, to be further developed. In this paper, self-healing hyperbranched poly(aroxycarbonyltriazole) based on such mechanism were prepared by our developed metal-free click polymerization of simplified dipropiolate and triazide. Thanks to their excellent processability and film-forming ability, high quality homogeneous films free from defects were obtained by casting. The cut films could be healed by stacking or pressing the halves together at room temperature and elevated temperature. Thus, this design concept for self-healing materials should be generally applicable to other hyperbranched polymers with reactive groups on their peripheries.

Full text of DOI:10.1007/s11426-016-0251-y

SCIENCE CHINA
Chemistry
• ARTICLES •
• SPECIAL TOPIC • Frontiers in Polymer Science
doi: 10.1007/s11426-016-0251-y
Self-healing hyperbranched polytriazoles prepared by metal-free
click polymerization of propiolate and azide monomers
Xin Wang1, Rongrong Hu1, Zujin Zhao1, Anjun Qin1* & Ben Zhong Tang1,2*
1Guangdong Innovative Research Team, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology,
Guangzhou 510640, China
2Department of Chemistry, Hong Kong Branch of National Engineering Research Center for Tissue Restoration & Reconstruction,
The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
Received June 5, 2016; accepted June 27, 2016; published online October 26, 2016
The last decade has witnessed the quick develop of self-healing materials. As a newborn strategy, the alternative of irreversible
covalent bond formation is, however, to be further developed. In this paper, self-healing hyperbranched poly(aroxycarbony-
ltriazole) based on such mechanism were prepared by our developed metal-free click polymerization of simplified dipropiolate
and triazide. Thanks to their excellent processability and film-forming ability, high quality homogeneous films free from de-
fects were obtained by casting. The cut films could be healed by stacking or pressing the halves together at room temperature
and elevated temperature. Thus, this design concept for self-healing materials should be generally applicable to other hyper-
branched polymers with reactive groups on their peripheries.
self-healing, hyperbranched polytriazole, metal-free click polymerization, film
Citation:
Wang X, Hu R, Zhao Z, Qin A, Tang BZ. Self-healing hyperbranched polytriazoles prepared by metal-free click polymerization of propiolate and
azide monomers. Sci China Chem, doi: 10.1007/s11426-016-0251-y
healing agents are needed: extrinsic and intrinsic self-heal-
1 Introduction
ing materials [8]. The former rely on the release of healing
agents and could be divided into several types such as hol-
low-fiber, nanoparticle, microcapsule, microvessel and car-
bon nano-tube self-healing materials [9]. This method pre-
ponderates in the easy performance and efficiency, but it
can not be repeated and the import of self-healing agents
limits its mechanical properties. On the other hand, the lat-
ter brings into effect with the help of reversible covalent
bonds and/or non-covalent bonds [10–12]. Nowadays, re-
search on the intrinsic self-healing materials has attracted
much more attention than their counterpart because of their
repeatability in healing process and no bother to consider
the compatibility of healing agents [13–18]. However, such
materials usually decrease its mechanical properties at ele-
vated temperature, and suffer from the complicated prepara-
tion process. For example, materials healed via the Diels-
The broken trees can regrow, the bleeding wounds can re-
cover, the annoying bruises can restore. The nature has the
unique ability to rebuild damages through a cascade of
complicated biochemical events, which used to be called as
miracle, and now should be called as self-healing property.
Inspired by nature, scientists have spared no effort to learn
from it and to mimic the self-healing process. For now, sev-
eral self-healing materials have been designed and devel-
oped, among which, polymeric materials are the most stud-
ied due to their excellent property of functionalization and
modification [1–7]. In general, there are mainly two kinds
of artificial healable polymers differentiated by whether
*Corresponding authors (email: msqinaj@scut.edu.cn; tangbenz@ust.hk)
© Science China Press and Springer-Verlag Berlin Heidelberg 2016
chem.scichina.com link.springer.com

2
Wang et al. Sci China Chem December (2016) Vol.59 No.12
Alder reaction will dissociate at temperature higher than
120 °C [19]. Therefore, it remains a big challenge to design
intrinsic self-healing materials with good and stable me-
chanical properties, as well as facile preparation process.
It is worth mentioning that irreversible covalent bond
formation strategy has a great potential to become the ideal
solution to repair the damage and enhance the mechanical
property of the intrinsic self-healing materials simultane-
ously. However, this approach needs to be further devel-
oped [20–22]. In the reported systems, the fulfillment of
self-healing needs to combine multiple components which
will complicate the manipulation procedures unquestiona-
bly. For example, Urban and coworker [21,23] have report-
ed a photo-healable irreversible covalent bonded heteroge-
neous polyurethane networks based on oxetane-substituted
derivative of chitosan, which could not formed until the
addition of the components of hexamethylene diisocyante
and polyethylene glycol. Thus, it will be an exciting and
promising research area to simplify the preparation process
and to be practically applicable.
high molecule weights and regio-regularity in high yields.
Thanks to their topological global structures and remaining
unreacted aroylacetylene and azide groups on the peripher-
ies, these hb-PATAs exhibited unique self-healing ability
but without addition of other component, such as catalysts
and cross-linkers [32–34].
Though the alkyne-azide click polymerization have al-
ready been used in the preparation of self-healing polytria-
zoles, the efforts were mainly paid on the Cu(I)-catalyzed
systems [35–40]. For instance, Binder and coworkers
[35,36] have applied this reaction to prepare self-healing
polymers with microcapsule self-healing strategy. However,
due to the residuary catalyst additives, the systems are het-
erogeneous, which reduced the healing efficiency. In our
aforementioned work, we reported an irreversible self-
healing strategy based on hb-PATAs [41], which greatly
simplifies the healing manipulation and facilitates the prac-
tical application. However, the aroylacetylenes have to be
prepared using high reactive reagent and toxic heavy metal
or Jones reagent via two reaction
oxidants such as MnO2
Our ongoing research projects have shone light into this
emerging area. We have been interested in developing new
polymerizations based on triple-bond building blocks and
have a variety of polymers with linear and topological
structures successfully synthesized [24]. Along this line, the
click polymerizations, such as transition metal-catalyzed
azide-alkyne click polymerization, metal-free click poly-
merization (MFCPs) of azides and activated alkynes as well
as alkyens and activated azides, and organic compound cat-
alyzed click polymerization of aromatic alkynes and azides
were successfully established and functional polytriazoles
with linear and hyperbranched structures were prepared
[25–31]. For example, the MFCP of aroylacetylene and az-
ide monomers under mild reaction conditions readily pro-
duced hyperbranched poly(aroyltriazole)s (hb-PATAs) with
steps under harsh reaction conditions, which will limit the
application of hb-PATAs in self-healing area.
In this paper, we report a simplified irreversible cova-
lent-bond self-healing system based on hyperbranched
poly(aroxycarbonyltriazole) (hb-PACT), which enjoys the
same feature as hb-PATAs, but the propiolate monomer
could be facilely prepared from commercially available
starting materials by one-step and one-pot reaction under
ambient conditions (Scheme 1) [42]. Similar to hb-PATAs,
hb-PACTs possess good film-forming ability and their films
are homogeneous and could be healed without any additive
at room temperature and elevated temperature, which will
extremely simplify the whole procedure from the prepara-
tion of monomers and polymers to the realization of self-
healing property.
Scheme 1 Synthetic route to hyperbranched poly(aroxycarbonyltriazole) of hb-PI.

Wang et al. Sci China Chem December (2016) Vol.59 No.12
3
ν (cm–1): 3239 (≡C–H stretching), 2945, 2112 (C≡C
2 Experimental
stretching), 1698 (C=O stretching), 1477, 1251, 966, 772,
1
713. H NMR (500 MHz, CDCl3), δ (TMS, ppm): 4.20 (t,
2.1 Materials
4H), 2.88 (s, 2H), 1.71 (m, 4H), 1.42 (m, 4H). 13C NMR
(125 MHz, CDCl3), δ (TMS, ppm): 152.7, 75.1, 74.8, 66.1,
28.2, 25.4. HRMS: m/z calculated for C12H14O4Na [M+Na]+=
245.0790; found=245.0784.
Toluene was distilled from sodium benzophenone ketyl in
an atmosphere of nitrogen prior to use. N,N-dimethyl-
formamide (DMF) was pre-dried over calcium hydride, dis-
tilled under reduced pressure, and kept under nitrogen. Oth-
er solvents were purified by standard methods. All reagents
were commercially available and were used as received
without further purification.
2.4 Polymer synthesis
The polymerization of triazide 1 and dipropiolate 2 were
carried out in air, unless otherwise stated. The experimental
procedures for the MFCP are shown below.
2.2 Instruments
In a 15 mL Schlenk tube were placed 0.2 mmol of 1 and
0.3 mmol of 2. Then, freshly distilled DMF (1.2 mL) was
injected into the tube to dissolve the monomers. After stir-
ring at 70 °C for 6 h, the reaction mixture was diluted with
10 mL of chloroform and added dropwise into 300 mL of
hexane through a cotton filter under stirring. The precipi-
tates were allowed to stand overnight and then collected by
filtration. The polymer was washed with hexane and dried
to a constant weight at ambient conditions. hb-PI was ob-
Infrared (IR) spectra were taken on a Bruker Vecrtex 70
(Germany) spectrometer as thin films on KBr pellets. H
1
and 13C NMR spectra were recorded on Bruker AV 500
NMR (Germany) spectrometers in CDCl3 using tetrame-
thylsilane (TMS; δ=0 ppm) as internal reference. Relative
weight-average (Mw) and number-average molecular
weights (Mn) of the polymers and their polydispersity indi-
ces (PDI, Mw/Mn) were estimated by a Waters 1515 gel
permeation chromatography (GPC) system (USA), using a
set of monodispersed linear polymethyl methacrylate
(PMMA) as calibration standards and DMF-0.05 M LiBr as
the eluents at a flow rate of 1.0 mL/min.
tained in 90.3% yield as white powder. Mw
9800, Mw/Mn
2.95 (GPC, determined in DMF-0.05 M LiBr on the basis of
PMMA calibration); fraction of 1,4-isomers in the polymer
88.5%; IR (thin film), ν (cm–1): 3133, 2937, 2098 (C≡C
and N3 stretching), 1718 (C=O stretching), 1542, 1460,
1
1350, 1227, 1041, 774. H NMR (500 MHz, CDCl3), δ
2.3 Monomer preparation
(TMS, ppm): 7.88, 7.60, 5.94, 5.73, 4.51, 4.19, 2.88, 2.45,
1.72, 1.43. 13C NMR (126 MHz, CDCl3), δ (TMS, ppm):
152.8, 140.3, 139.7, 138.3, 132.6, 130.7, 129.7, 75.3, 74.7,
66.2, 53.4, 49.3, 48.9, 28.4, 25.4, 16.6.
1,3,5-Tris(azidomethyl)-2,4,6-trimethylbenzene (1) was pr-
epared according to the experimental procedures described
in our previous work [43]. The diyne of dipropiolate (2) was
prepared by esterification of diol (3) with propiolic acid (4)
in the presence of TsOH (Scheme 2). Detailed experimental
procedures are given below.
2.5 Self-standing film preparation
In a 250 mL round-bottom flask equipped with a Dean-
Stark apparatus were added 4.20 g (60 mmol) of propiolic
acid (3), 2.36 g (20 mmol) of 1,6-hexanediol (4), and 1.14 g
(6 mmol) of TsOH in 100 mL of dry toluene. After refluxed
for 48 h with constant removal of yielded water, the reac-
tion mixture was concentrated, and the residues were dis-
solved in 100 mL of dichloromethane (DCM). The organic
phase was washed with 5% aqueous NaHCO3 solution (30
mL×3) and water (50 mL×1) and then dried over Na2SO4
overnight. After filtration and solvent evaporation, the crude
product was purified by a silica gel column using petroleum
ether/ethyl acetate (6:1, v/v) as eluent. Hexane-1,6-diyl di-
propiolate (2) was obtained in 83.0% yield (3.69 g) as a
white solid. Melting point: 46.9–47.7 °C. IR (thin film),
The films of hb-PI were prepared by solution casting meth-
od. 300 mg of hb-PI was dissolved in 15 mL 1,2-dichloro-
ethane. The solution was poured into a flat-bottomed PTFE
mould with length of 80 mm, width of 30 mm, and allowed
to dry at room temperature for 36 h. Then, the films were
further dried at 40 °C overnight to remove residual solvents.
3 Results and discussion
3.1 Synthesis
The dipropiolate 2 was facilely prepared in high yield of
83.0% from commercially available aliphatic diol 3 and
propiolic acid 4 under mild condition via one-step esterifi-
cation reaction in one pot (Scheme 2). By using the
polymerization conditions we reported previously, hb-PI
with Mw of 9800 was also prepared from the monomers 1
and 2 in DMF at 70 °C for 6 h in air with molar ratio of 2:3
in 90.3% yield (Scheme 1). The resulting polymer of hb-PI
Scheme 2 Synthetic route to diyne 2.

4
Wang et al. Sci China Chem December (2016) Vol.59 No.12
is soluble in common used organic solvents such as tetrahy-
drofuran, chloroform and 1,2-dichloroethane which will
facilitate its structural characterization.
3.2 Structural characterization
The monomers and polymers were characterized by spec-
troscopic methods, and satisfactory results corresponding to
their expected molecular structures are obtained.
The IR spectra of hb-PI and its monomers are given in
Figure 1.
Monomer 1 shows absorption bands at 2101 cm–1, which
is associated with the azido group. The strong absorption
bands at 3247 and 2122 cm–1 are due to its C–H and C≡C
stretching vibrations, respectively. All these absorption
bands are still observed at similar wavenumbers but become
weaker in the spectrum of hb-PI, suggesting that most of the
ethynyl and azido groups of the monomers have been con-
verted into the triazole rings of the polymer by the MFCP.
Moreover, it also reflects the possibility to further reacted to
realize self-healing ability.
1
In addition, we performed the H and 13C NMR analysis
1
of monomers and hb-PI in CDCl3. Figure 2 shows the H
NMR spectra of hb-PI and its monomers. All resonance
peaks of polymer and monomers are assignable. The reso-
nances of the methylene protons adjacent to the azido
groups of 1 and the ethynyl protons of 2 at δ=4.50 and 2.88
ppm, respectively, become weaker after MFCP. Meanwhile,
new peaks resonated at δ=7.90–7.75, 5.94, and 5.74 ppm are
observed in the spectrum of hb-PI. The peaks at δ=7.90–
7.75 ppm are associated with the resonances of the protons
in the triazole rings in the 1,4- and 1,5-isomers, which are
Figure 2 1H NMR spectra of monomer 1 (A) and 2 (B) and their polymer
hb-PI (C) in CDCl3. The solvent and water peaks are marked with asterisks
(color online).
hard to discriminate. While, the peaks at δ=5.94 and 5.74
ppm stemmed from the neighboring methylene groups in
the 1,5- and 1,4-isomeric units, respectively, are well-sepa-
rated, from which the fraction of 1,4-isomer was calculated
to be 88.5%. The results indicate that part of the ethynyl and
azido groups of the monomers have been transformed into
the triazole rings of the polymer by MFCP, further con-
firming the conclusion drawn from the IR spectra analysis.
The 13C NMR spectrum of hb-PI (Figure 3) shows weak
resonance peaks of acetylenic carbon atoms at δ=74.8 and
72.7 ppm compared to those of its monomer. Furthermore,
new peaks corresponding to the absorptions of the triazole
carbons are observed at δ=140.0 and 138.2 ppm. These re-
sults also indicate that the azide of 1 and ethynyl groups of
2 have been converted into triazole rings in the polymer by
MFCP.
3.3 Self-healing of the polymer films
Differ from traditional hyperbranched polymers, hb-PI fea-
tures excellent film-forming ability, which enables us to
prepare self-standing and transparent homogeneous thick
films with ease. Thus, defect-free films with thickness of
Figure 1 IR spectra of monomers 1 (A) and 2 (B) and their polymer
hb-PI (C).

Wang et al. Sci China Chem December (2016) Vol.59 No.12
5
films were halved by a razor blade and the two parts were
stacked by overlapping length of 5 mm, and heated at cer-
tain temperature and with certain time. To investigate the
effect of heating temperature and time course on the self-
healing procedure, we particularly studied both of the con-
ditions (Table 1), and chose the suitable one for further test.
We first investigated whether the hb-PI film could be
self-healed at room temperature. To our surprise, hb-PI
films started to show self-healing property when placed
over 12 h, but still not strong enough to bear weight when
we did the brief mechanical test until the time prolong to no
less than 16 h (Figure 4(b)). Increasing the temperature will
greatly shorten the healing time. When the temperature in-
creased to 100 °C, the film was completely self-healed after
2 h and was strong enough to perform the standard me-
chanical test. Thus, we finally chose 100 °C as the best con-
dition for following test.
In our previous work, we have chosen the film overlap-
ping length of 5 mm for the self-healing. In this work, we
are curious about whether the overlapping length is critical
to the realization of self-healing. So we did a further test
about the effect of overlapped length of the film on the self-
healing property (Table 2).
We can find from Table 2 that with enhancing overlap-
ping length of the films from 2 to 5 mm, the tensile strength
of the films almost doubled and then hold steady. As the
overlapping length of the film is less than 5 mm, the self-
healed film has a great probability to laniate at the overlap-
ping area when tested the tensile strength, which seriously
decreased the average tensile strength. This result suggests
Figure 3 13C NMR spectra of monomer 1 (A) and 2 (B) and their poly-
mer hb-PI (C) in CDCl3. The solvent and water peaks are marked with
asterisks (color online).
Table 1 Effect of temperature and time course on self-healing of the files
of hb-PI a)
Entry
T (°C)
r.t. c)
r.t.
t (h)
8
Result a)
×
×√
√
1
2
3
4
5
6
7
8
9
12
16
4
r.t.
×√
√
50
50
6
Figure 4 Self-healing on the surface of hb-PI film. (a) The as-prepared
film from hb-PI by mould; (b) the self-healed film with overlapping length
of 5 mm after heated at r.t. for 16 h. The thickness of the film is 70±10 μm.
×√
√
75
2
75
4
×
100
100
1
2
√
70±10 μm were fabricated by casting (Figure 4(a)).
a) The overlapped length is 5 mm for all the films; b) √=completely
self-healed; ×=did not self-healed; ×√=preliminary self-healed; c) r.t.=
room temperature.
In our previous work, we have already established a self-
healing system based on hb-PATAs. According to the
structural characterization of hb-PATAs, the unreacted az-
ide and ethynyl groups on their periphery will remain on the
surface of their films and sticks, which could further react
upon heating and show the irreversible covalent bonded
self-healing property. The hb-PI also contains unreacted
azide and ethynyl groups on its periphery, implying that its
films could exhibit the self-healing property similar to
hb-PATAs. Thus, we investigated this property in this work.
We first prepared dried films of hb-PI in mould, then the
Table 2 Effect of overlapping length of the film on self-healing
Entry Overlapping length (mm)
Tensile strength (MPa) a) Result b)
1
2
3
2
5
21.16
40.53
42.38
√
√√
√√
10
a) Average results of 4 tests; b) the films were heated at 100 °C for 2 h;
√=exhibiting self-healing property but not effective, √√=exhibiting
self-healing property and effective.

6
Wang et al. Sci China Chem December (2016) Vol.59 No.12
that when the overlapping length of the film is less than
5 mm, the self-healed film was not good enough for further
mechanical test. Moreover, increasing the overlapping
length over 5 mm has little effect on the tensile strength. So
we finally choose 5 mm as the preferable overlapping
length.
tained two self-healed areas and performed the same mech-
anical test. The results show that the self-healing behaviors
are the same as the former test and the broken site was not
at the healed area, indicative of repeatable self-healing pro-
cedures.
Finally, we tested the mechanical property of the self-
healed films and compared them with the pristine films
without cut-and-cure procedures. As shown in Figure 5, the
Young’s modulus and the fracture stress of healed films are
all higher than those of the pristine films treated under the
same experimental conditions, indicating that the self-
healing process could reinforce the mechanical property of
the film simultaneously. Moreover, the broken sites of the
films were near the fixture of the testing machine instead of
the healed area, revealing that the healed area has a stronger
mechanical property, further demonstrating that the self-
healing process is effective and can prevent the films from
breaking from the same point again.
It is particularly worth noting that in our previous work,
we have assumed that the unreacted azide and ethynyl
groups left in the healed films could be further reacted upon
heating. To test the possibility for the self-healed films to be
re-healed upon broken, and take practical application into
consideration, we carried out additional experiments. First,
an as-prepared film was cut and the two parts were stacked
by overlapping length of 5 mm, then the overlapping area
instead of the whole film was heated at 100 °C for 2 h. Af-
terwards, the self-healed film was cut again at another site
and stacked by overlapping length of 5 mm, and repeated
the heating procedure. Finally, we got a film which con-
4 Conclusions
In this paper, we report a simplified irreversible covalent-
bond self-healing system based on hb-PACTs prepared by
the powerful MFCP of propiolate and azide monomers. It is
worth noting that the propiolate and azide monomers could
be facilely prepared from commercially available starting
materials by one-step and one-pot reaction under ambient
conditions. The obtained hb-PI possesses excellent film-
forming ability and could be fabricated into self-standing,
transparent and homogeneous thick films free from defects
by simple casting process. Taking advantage of the remain-
ing azide and ethynyl groups on the periphery of hb-PI, the
cut halves of the films could be healed by stacking or
pressing together at room temperature and elevated temper-
ature. The self-healed films show higher mechanical
strength than their pristine films under the same experi-
mental conditions. Moreover, the films could realize re-
peatable self-healing behaviors. Thus, we believe that our
design concept for self-healing materials should be general-
ly applicable to other hyperbranched polymers with reactive
groups on their peripheries.
Acknowledgments This work was supported by the National Natural
Science Foundation of China (21525417, 21490571, 21222402), the key
project of the Ministry of Science and Technology of China
(2013CB834702), the National Program for Support of Top-Notch Young
Professionals, the Fundamental Research Funds for the Central Universi-
ties (2015ZY013), and the Innovation and Technology Commission of
Hong Kong (ITC-CNERC14SC01). A.J. Qin and B.Z. Tang thank the
support from Guangdong Innovative Research Team Program
(201101C0105067115).
Conflict of interest The authors declare that they have no conflict of
interest.
1
2
Syrett JA, Becer CR, Haddleton DM. Polym Chem, 2010, 1: 978–987
Hager MD, Greil P, Leyens C, Schubert US. Adv Mater, 2010, 22:
5424–5430
3
4
5
6
7
8
Murphy EB, Wudl F. Prog Polym Sci, 2010, 35: 223–251
Urban MW. Prog Polym Sci, 2009, 34: 679–687
Wu DY, Meure S, Solomon D. Prog Polym Sci, 2008, 33: 479–522
Yang Y, Urban MW. Chem Soc Rev, 2013, 42: 7446–7467
Habault D, Zhang H, Zhao Y. Chem Soc Rev, 2013, 42: 7244–7256
Yan XY, Xu DH, Chen JZ, Zhang MM, Huang FH. Polym Chem,
2013, 4: 3312–3322
9
Li HY, Zhang LB, Li J, Wang J. Chem Ind Eng Prog, 2014, 33:
133–139
Figure 5 Stress-strain curves of hb-PI films. (a) The as-prepared film; (b)
the self-healed film at room temperature for 16 h; (c) the pristine film after
heating at 100 °C for 2 h; (d) the self-healed film after heating at 100 °C
for 2 h. The test was carried out at room temperature with humidity of 52%
at a pulling rate of 2 mm/min by SANS CMT 4204 (China) instrument
with the standard length of 50 mm. The sizes of the films are 15 mm in
width, 80 μm in thickness, and 60 mm in length.
10 Li HY, Zhang LB, Wang J. Chem Ind Eng Prog, 2012, 31: 1549–
1554
11 Ji S, Cao W, Yu Y, Xu HP. Adv Mater, 2015, 27: 7740–7745
12 Ji X, Huang FH. Sci China Chem, 2015, 58: 436–437
13 Chen X, Dam MA, Ono K, Maj A, Shen H, Nutt SR, Sheran K, Wudl
F. Science, 2002, 295: 1698–1702

Wang et al. Sci China Chem December (2016) Vol.59 No.12
7
14 Cordier P, Tournilhac F, Souli’e-Ziakovic C, Leibler L. Nature,
2008, 451: 977–980
15 Amamoto Y, Kamada J, Otsuka H, Takahara A, Matyjaszewski K.
Angew Chem Int Ed, 2011, 50: 1660–1663
16 Burattini S, Greenland BW, Chappell D, Colquhoun HM, Hayes W.
Chem Soc Rev, 2010, 39: 1973–1985
17 Chen Y, Kushner AM, Williams GA, Guan Z. Nat Chem, 2012, 4:
467–472
BZ. Adv Funct Mater, 2009, 19: 1891–1900
30 Li, HK, Wang J, Sun JZ, Hu RR, Qin AJ, Tang BZ. Polym Chem,
2012, 3: 1075–1083
31 Wei Q, Deng HQ, Cai YB, Lam JWY, Li J, Sun JZ, Gao M, Qin AJ,
Tang BZ. Macromol Rapid Commun, 2012, 33: 1356–1361
32 Gao C, Yan DY. Prog Polym Sci, 2004, 29: 183–275
33 Banerjee S, Komber H, Voit B. Macromol Chem Phys, 2009, 210:
1272–1282
18 Ling J, Rong MZ, Zhang MQ. Chinese J Polym Sci, 2014, 32: 1286–
1297
34 Wu WB, Tang RL, Li QQ, Li Z. Chem Soc Rev, 2015, 44: 3997–
4022
19 Guimard NK, Oehlenschlaeger KK, Zhou J, Hilf S, Schmidt FG,
Barner-Kowollik C. Macromol Chem Phys, 2012, 213: 131–143
20 Burattini S, Greenland BW, Chappell D, Colquhoun HM, Hayes W.
Chem Soc Rev, 2010, 39: 1973–1985
35 Gragert M, Schunack M, Binder WH. Macromol Rapid Commun,
2011, 32: 419–425
36 Schunack M, Gragert M, Binder WH. Macromol Chem Phys, 2012,
213: 205–214
21 Ghosh B, Chellappan KV, Urban MW. J Mater Chem, 2011, 21:
14473–14486
22 Billiet S, Camp WV, Hillewaere XKD, Rahier H, Prez FED. Poly-
mer, 2012, 53: 2320–2326
23 Ghosh B, Urban MW. Science, 2009, 323: 1458–1460
24 Liu JZ, Lam JWY, Tang BZ. Chem Rev, 2009, 109: 5799–5867
25 Qin AJ, Lam JWY, Tang BZ. Chem Soc Rev, 2010, 39: 2522–2544
26 Qin AJ, Lam JWY, Tang BZ. Macromolecules, 2010, 43: 8693–8702
27 Li HK, Sun JZ, Qin AJ, Tang BZ. Chinese J Polym Sci, 2012, 30:
1–15
28 Qin AJ, Jim, CKW, Lu W, Lam JWY, Häussler M, Dong YQ, Sung
HHY, Williams ID, Wong GKL, Tang BZ. Macromolecules, 2007,
40: 2308–2317
37 Michael P, Binder WH. Macromolecules, 2012, 45: 3335–3345
38 Sheng X, Mauldin TC, Kessler MR. J Polym Sci Part A: Polym
Chem, 2010, 48: 4093–4102
39 Yuan JC, Fang XL, Zhang LX, Hong GN, Lin YJ, Zheng QF, Xu YZ,
Ruan YH, Wen WG, Xia HP, Chen GH. J Mater Chem, 2012, 22:
11515–11522
40 Wei Q, Wang J, Shen XY, Zhang XA, Sun JZ, Qin AJ, Tang BZ. Sci
Rep, 2013, 3: 1093
41 Wu HQ, Dong WH, Wang ZT, Yao BC, Chen M, Sun JZ, Qin AJ,
Tang BZ. Sci China Chem, 2015, 58: 1748–1752
42 Li HK, Wu HQ, Zhao EG, Sun JZ, Qin AJ, Tang BZ. Macromole-
cules, 2013, 46: 3907–3914
43 Qin AJ, Lam JWY, Tang L, Jim CKW, Zhao H, Sun JZ, Tang BZ.
Macromolecules, 2009, 42: 1421–1424
29 Qin AJ, Tang L, Lam JWY, Jim CKW, Yu Y, Zhao H, Sun JZ, Tang